On the advantages of nickel-base super-alloy laser cladding by direct powder injection

Stellite was laser-clad on nickel-base super-alloy substrates by Direct Powder Injection (DPI). Numerical estimations showed that the gas jet (carrying the particles injected) to be supplies the main force affecting and particularly stirring, the melt pool. The value of this force is at least 1 and even more possibly 2 orders of magnitude larger than of the surface tension. Optical and electron microscopy results show that grains in the laser-clad layer are almost one order of magnitude smaller than those of the initial material. This is a result of the high cooling rate of the melt characteristic of laser cladding by DPI, and it, in turn, resulted in a very high micro-hardness of the laser clad layer (720HV – 840HV) as against 400HV of the original material and 420HV of the plasma clad layer. It is further shown that the laser-clad layer and its interface with the substrate are free of the micro-cracks and pores usually typical of plasma cladding. It is also shown that the interface between the cladding ...